Within the residential and commercial heating industry there has been a great need to increase the efficiency of pelletized fuel burning furnaces. Numerous furnaces, created in an attempt to meet that need, have been disclosed in issued patents.
Wynn (U.S. Pat. No. 2,034,890) discloses a stoker having a vertically disposed cylindric chamber into which fuel is fed. The stoker cylinder is surrounded by an air chamber with a tuyere cover. The tuyere cover has a plurality of openings for discharging air into a combustion chamber. A separate conduit feeds air from a fan to the air chamber.
Stark (U.S. Pat. No. 2,067,583) discloses a stoker which feeds coal particles into a furnace box. Air for combustion is blown by a fan through twyers or orifices in a housing surrounding a combustion area.
Harris (U.S. Pat. Nos. 4,323,017 and 4,385,566) disclose various burner apparatus into which pelletized wood waste is fed from a hopper through a conduit by an auger screw. The screw is housed in a fuel supply conduit. Forced air is delivered through a tube to a plurality of apertures in the bowl of the burner.
Collins et al. (U.S. Pat. No. 4,565,184) describes a heater in which particulate fuel is fed by an auger to a retort. Air entering through a delivery tube passes into the retort through discharge openings located within the periphery of the retort manifold to support primary combustion. Secondary air is supplied through another set of discharge openings from an auxiliary manifold.
These disclosures are believed to illustrate the general scope of the prior art related to pelletized or particulate fuel burning furnaces. The applicant submits that these disclosures, taken alone or together, do not teach the combination of concepts embodied in this invention.